The technical scope of the present invention is that of sabots for fin-stabilized projectiles, in particular large caliber.
Fin-stabilized projectiles are classically constituted by a penetrator made of a heavy material such as tungsten or uranium alloy to which a sabot is added to ensure its propulsion through the gun barrel.
The sabot is generally axisymmetrical and is made of aluminum alloy, either by machining a heat treated wire bar, or by impact forging.
Mostly of the time, the sabot is constituted by three segments linked to the penetrator by threading or grooves allowing the penetrator to be driven in translation. The sabot segments are joined together by a belt that also acts as a seal between the gun barrel and the sabot. Known sabots generally incorporate three zones: the body itself to retain and drive the penetrator, the thrust plate, of the same calibre as the barrel with respect to which it guides the sabot and which withstands the pressure generated by the gases, and lastly the front pocket.
The front pocket generally presses against the barrel walls and participates in guiding the projectile.
Upon exiting the barrel, the front pocket receives the aerodynamic pressure which results in a stress perpendicular to the penetrator that is enough to break the retaining rings and belts and to separate the sabot segments so as to release the penetrator which alone continues its ballistic flight towards the target.
We understand that the sabot constitutes a dead weight that must be discarded as soon as possible and which additionally consumes available kinetic energy.
Trials have been carried out to reduce the sabot""s mass.
Thus, patent GB-A-2251676 describes a sabot whose segments are constituted by laminar elements of a composite material whose fibers are oriented. The drawback of such an arrangement lies in the multitude of elements composing the sabot and making it difficult to manufacture. U.S. Pat. No. 4,958,571 is known that describes a particular sabot comprising continuous filaments and in which the rear of the penetrator is covered by means of these filaments, which are long enough to reduce the bending stress on the sabot. It is specified in this patent that the fibers must break upon exiting the barrel in order to separate the sabot.
All the attempts made to date have lead to sabots of a non-negligible masse since said sabot must ensure both the driving of the penetrator, its guidance in the barrel and its resistance to the firing constraints.
The minimal section of the sabot is calculated by considering that the projectile follows a perfectly rectilinear trajectory and that the pressure load is perfectly axisymmetrical. This results in a sabot being defined that is not always transversally rigid enough, requiring material to be added either by increasing the diameter or by adding ribs.
The aim of the present invention is to propose a sabot having a reduced mass, that is easy to manufacture and requires no reinforcing means to ensure its transversal rigidity.
The invention thus relates to a sabot for fin-stabilized ammunition composed of calibrated segments assembled around a sub-calibrated penetrator, wherein it comprises at least three longitudinal bars of a substantially constant width and each having indentations co-operating with an external profile of the penetrator to allow it to be driven, as well as a calibrated thrust plate integral with the bars.
The bars may have a prismatic cross section.
The bars will advantageously be of a thickness similar to the penetrator""s diameter.
Each bar may carry a stud on its front part to provide guidance in the gun barrel.
The thrust plate may have a sealing belt that also joins the bars to the penetrator.
According to one embodiment, the thrust plate may be divided into at least three adjoining sectors, each bar carrying one sector of the thrust plate.
Each sector may in this case incorporate a radial notch that caps a matching notch carried on the bar.
Bars and sectors may be made of the same material. Each sector may be made as a single part with its bar.
According to another embodiment, the thrust plate may be divided into at least three adjoining sectors, each sector incorporating a footplate applied to the penetrator and integral with a calibrated wall, the walls of two adjoining sectors delimiting a gap to receive a bar.
Each bar may in this case comprise a recess on its face applied to the penetrator that caps the footplates of two adjoining sectors.
Each bar may incorporate two radial slots reducing its thickness at a median part, such slots receiving the walls of two sectors of the thrust plate.
In all the embodiments, the bars may be made of a composite material whereas the sectors will be made of a metallic material.
A first advantage of the sabot according to the invention lies in the substantial reduction of the sabot""s mass.
Another advantage lies in the ease of manufacture of the sabot leading to lower manufacturing costs.
Another advantage lies in the fact that each sabot segment does not have to be specially machined.